Heretofore, if a stenosis has occurred in a vessel of a living body, in particular the blood vessel, such as artery, a balloon forming portion provided in the vicinity of the distal end of a balloon catheter is inserted into this stenosis portion, and the wrapped balloon forming portion is inflated to expand the stenosis portion of the blood vessel to improve the blood flow in the vessel. This operation is termed percutaneous transluminal angioplasty (PTA).
However it has been known, if the PTA is applied, stenosis tends to be reproduced at a high probability in the once stenosis portion.
To prevent this restenosis, the technique of implanting a tubular stent in the site applied PTA has been used. This stent is inserted into the blood vessel as it is contracted in diameter, and subsequently expanded so as to be implanted in the blood vessel to support the blood vessel wall from its inside, and to prevent occurrence of restenosis in the blood vessel.
As such sort of the stent, a stent comprised a tubular metal member provided with an incision to permit its expansion or contraction in diameter has been known.
Metal stent may cause a reaction against a foreign substance by remaining for a prolonged time in a living body. Hence, it is not desirable or proper to remain metal stent in the living body semi-permanently. Moreover, surgical operations are needed to remove the metal stent once the stent is implanted in the living body, thus imposing a severe load on the patient.
To solve such inherent problem with the metal stent, the present inventor has proposed a stent formed of a biodegradable polymer in Patent Publications of WO92/15342 and WO00/13737. A stent formed of a biodegradable polymer has also been proposed in JP Laid-Open Patent Publication H-11-57018.
Recently, many reports have been made on the effect of a so-called drug eluting stent, which a drug is locally released from a stent implanted in the living body to restrain hyperplasia of neointima. The present inventor has proposed in the Publication of WO2004/028615 a so-called drug eluting stent in which a drug is locally released from to restrain hyperplasia of neointima.